The present invention relates to the field of integrated circuits in general, and more particularly, to methods of forming features of integrated circuits and features so formed.
It is known to use light sources, such as lasers, as a part of a photolithographic process of fabricating integrated circuits. For example, it is known to use i-line and KrF excimer lasers to form patterns on integrated circuit substrates which are used to form integrated circuit devices. As the size of integrated circuit features decreases, lasers which produce light having a relatively short wavelength may be used in the photolithographic process to form the features. For example, ArF and F2 excimer lasers may be used to form integrated circuit features that are smaller than those formed using the i-line or KrF excimer lasers discussed above.
It is also known to select photoresist materials (used to form the patterns for the features to be formed) based on the type of laser used during the photolithographic process. For example, photoresist materials, such as poly(meth)acrylate, cyclo-olefin maleic anhydride(COMA) and polynorbornene, may be used in conjunction with ArF and F2 excimer lasers.
Scanning Electron Microscopy (SEM) may be used to measure the size of the features formed by the photolithographic process. For example, SEM may be used to confirm or measure a Critical Dimension (CD) of the features formed by the process. However, one of the problems associated with the use of some photoresist materials, such as those discussed above in association with ArF excimer lasers, is that exposure to the SEM may cause phenomena referred to as line edge roughness (LER) and E-beam shrinkage.
FIG. 1 is a schematic diagram which illustrates E-beam shrinkage wherein the actual width of the feature formed by the photolithographic process is reduced as a result of exposure to the SEM. Moreover, the more that the feature is exposed to the SEM, the more the feature may shrink. For example, FIG. 2 is a graph that illustrates measurements of actual feature sizes measured using SEM. As shown in FIG. 2, as the number of top down SEM measurements is increased, the critical dimension of features formed using ArF can decrease in a range of 6% to 15% compared to the initial measurement of the feature using SEM.
E-beam curing has been proposed as a potential solution to the E-beam shrinkage problem discussed above. In particular, it is known to expose the features to an electron beam using a Focus Exposure Matrix (FEM) which is applied in doses to increase a crosslinking affect in the resist material used during the photolithographic process so that the resist material can be hardened before decomposition of the resist material can occur. Unfortunately, use of this E-beam technology may be expensive and increase the complexity of the process used to fabricate the integrated circuits.
FIG. 3 is a schematic diagram that illustrates the phenomenon referred to as LER. LER can occur due to inadequate homogeneity in the polymerization of the ArF resist material. The inadequate homogeneity can cause the resist material to harden so that the boundary between the hardened and unhardened resist material is rough or uneven. When the unhardened resist material is removed, the rough or uneven boundary between the hardened unhardened resist material causes the edges of the feature to be rough as shown in FIG. 3.
E-beam shrinkage and LER are further discussed in U.S. Pat. No. 6,319,853 to Ishibashi et al. entitled Method of Manufacturing a Semiconductor Device Using a Minute Resist Pattern, and a Semiconductor Device Manufactured Thereby (xe2x80x9cIshibashixe2x80x9d).
Embodiments according to the present invention can provide microelectronic features using water-soluble coatings on resist materials. Pursuant to these embodiments, a resist pattern, of a resist material, can be formed on a microelectronic substrate. A coating layer, including a water-soluble resin, is formed on the resist pattern, wherein the water-soluble resin and the resist material are miscible with one another and intermix to provide an intermixed layer comprising the resist material and the water-soluble resin between the resist pattern and a non-intermixed coating layer. The intermixed layer can be hardened and the non-intermixed coating layer can be removed from the hardened intermixed layer.
The hardened intermixed layer can reduce E-beam shrinkage and LER by protecting the underlying resist material, such as an ArF resist, an F2 (157 nm) resist, an Extreme Ultra Violet resist, or an X-ray resist, from the effects of E-beam radiation. The hardened intermixed layer can increase the width of the feature defined by the resist material by an amount equal to the hardened intermixed layer""s thickness. When the resist material and the hardened intermixed layer are exposed to the E-beam radiation, the shrinkage caused by the E-beam can be reduced compared to that of conventional systems.
In some embodiments according to the present invention, the coating layer includes a solution of the water-soluble resin having a concentration in a range between about 5% and about 10% by weight and at least one or more of a solution of a water-soluble crosslinking agent having a concentration in a range between about 1% and about 20% by weight or de-ionized water. In some embodiments according to the present invention, the coating layer is devoid of a crosslinking agent. In some embodiments according to the present invention, the coating layer is devoid of de-ionized water.
In some embodiments according to the present invention, the non-intermixed coating layer is removed from the hardened intermixed layer by rinsing the non-intermixed coating layer from the hardened intermixed layer using an aqueous medium that is devoid of a water-soluble organic solvent, such as isopropyl alcohol (IPA). In some embodiments according to the present invention, the non-intermixed coating layer is rinsed from the hardened intermixed layer xe2x80x9cusing an aqueous medium consisting essentially of de-ionized water.xe2x80x9d
In some embodiments according to the present invention, because of the water-solubility of the coating layer, the non-intermixed portion of the coating layer can be rinsed from the structure using, for example, only water and can avoid the use of water-soluble organic solvents (such as IPA) which solvents are used in some conventional approaches.
In some embodiments according to the present invention, the water-soluble resin is a pyrrolidone-based polymer such as an acrylic acid-based polymer, an alkyl amine-based polymer, an ammonium salt-based polymer, a maleic acid-based polymer, or a polyaromatic polymer.
In some embodiments according to the present invention, the pyrrolidone-based polymer includes at least one of a polyvinylpyrrolidone(PVP), a poly(1-vinylpyrrolidone-co-acrylic acid) or a poly(1-vinylpyrrolidone-co-2-dimethylaminoethyl methacrylate).
In some embodiments according to the present invention, the acrylic acid-based polymer includes at least one of a poly acrylic acid, a poly(acrylamide-co-acrylic acid) or a poly(acrylonitrile-co-acrylic acid).
In some embodiments according to the present invention, the alkyl amine-based polymer includes at least one of a poly(allylamine), a poly(dimethylamine-co-epichlorohydrin-co-ethylenediamine) or a polyethylenimine.
In some embodiments according to the present invention, the ammonium salt-based polymer includes at least one of a poly(acrylamide-co-diallyldimethylammonium chloride), a poly(diallyldimethylammonium chloride) or a poly(vinylbenzyl chloride) ammonium salt.
In some embodiments according to the present invention, the maleic acid-based polymer is poly(methyl vinyl ether-alt-maleic acid).
In some embodiments according to the present invention, the polyaromatic polymer includes at least one of a poly(styrene-co-maleic acid), a poly(styrenecarboxylic acid), a poly(styrenesulfonic acid) or a poly(hydroxystyrene-co-2-hydroxyethyl methacrylate).